Paul Walker crash: Vin Diesel, 'Fast and Furious' cast speak

Actor Paul Walker's "Fast and Furious" costars and others involved in the movie franchise spoke Monday about the fiery crash that killed him and a friend over the weekend.

Among the cast mates who made pilgramages to Walker's burgeoning makeshift memorial in Santa Clarita was Vin Diesel, who addressed the crowd using the public address system of a sheriff's department patrol car.

"If my brother were here today. And if he saw all the love you were bringing here. If he could see for himself that [you have] shown my brother love," Diesel told the crowd.

Authorities were still investigating what caused the crash, which occurred about 3:30 p.m. Saturday on Hercules Street, a normally quiet road with a 45-mph speed limit. Walker's friend, Roger Rodas, was driving the 2005 red Porsche Carrera GT when it slammed into a tree and concrete pole, bursting into flames and killing both men.

"It was 'Fast and the Furious,' that's what it is," witness and friend Jim Torp told fans and media at the crash site on Sunday. Both men were race car enthusiasts, Torp said, "both loved speed, both knew how to handle cars, and this had to happen."

Fellow "Fast and Furious" costar Tyrese Gibson broke down at the memorial on Sunday after leaving a single flower. F. Valentino Morales, a producer who had been working with Walker on “Fast and Furious 7,” also remembered the actor Sunday at the crash site.

“We were very close,” Morales told KTLA, adding that Walker was “the nicest guy in the world."

"Everybody loved him," Morales said. "He’ll be missed."

As news of the actor's death spread, hundreds of fans started streaming by the memorial on Sunday and Monday, leaving behind flowers, remembrances and photos. One fan left a green bottle of Castrol motor oil.

Alberto Ramirez, 19, of Downey was in Santa Clarita for a job interview and felt it was "the right thing to do" to come to the site.

"I was a fan since I was little watching his movies. I had to just stop by to take it all in. When I first heard it, I thought it was a hoax," he said.